Compared to single-layer graphene (SLG), multilayer graphene (MLG) and graphite films (GF) offer superior mechanical stability, tunable electrical conductivity, and lower manufacturing costs. However, during their preparation and transfer processes, defects such as vacancies, grain boundaries, wrinkles, and stacking disorder are inevitably introduced, and these defects have a critical impact on material performance. The defects such as vacancies, dopant atoms, and edges can enhance gas adsorption, catalytic activity, and ion storage capacity, while the defects such as grain boundaries and dislocations reduce electrical conductivity, strength, and thermal transport properties. Therefore, defect engineering mainly focuses on precisely controlling the type, density, and distribution of defects through methods such as ion implantation, plasma treatment, laser irradiation, and strain engineering, and on repairing them via high-temperature annealing or chemical methods. For applications requiring extremely high carrier mobility or thermal conductivity, nearly defect-free single-crystal MLG/GF can also be prepared, and applications of defect-engineered MLG or GF in corrosion protection, thermal management, energy storage, sensors, electronics, and quantum physics are discussed.